Prussian blue analogue functionalized magnetic microgels with ionized chitosan for the cleaning of cesium-contaminated clay.

To deal with regeneration of nuclear-waste-contaminated soil, it is important to develop new materials and techniques for effective removal of radioactive cesium ions from clay. We report herein a synergistic remediation method for cleaning cesium-contaminated clay by Prussian blue analogue-functionalized magnetic microgel along with ionized chitosan. The magnetic microgels were prepared by surface polymerization of 4-vinyl pyridine and styrene on magnetite nanoparticles and attachment of Prussian blue analogues by ligand exchange reaction. The adsorption of cesium ions by magnetic microgels in aqueous solution follows the second-order kinetics process. And the maximum adsorption capacity was determined to be 149.70 mg/g by Langmuir adsorption model. When ionized chitosan hydrochloride was mixed with cesium-contaminated clay, we found that 200 mg/g clay of chitosan hydrochloride can realize 87.6 % of cesium release from clay within 2 h. Further use of magnetic microgel adsorbents can adsorb 95.5 % free cesium ions in solution, achieving an overall 83.7 % cleaning efficiency from cesium-contaminated clays. The microgels can be regenerated effectively and recycled magnetically while keeping the adsorption capacity constant after multiple times of use. The underlying principle demonstrated in this work can be extended to remediation of other types of radionuclides or heavy-metal ions in contaminated soil.